Three modifications are commonly made to conventional anti-lock braking ("ABS") systems in order to integrate a traction control ("TC") function, namely, (i) the pump must be restructured so as to be a self-priming pump, (ii) provision must be made for providing fluid to the pump inlet, i.e. a "priming" valve, and (iii) providing the means of closing the circuit so that the pump can build pressure at the driven wheel brake higher than that originating from the master cylinder, a function normally provided by a "switching" valve. At least one of these valves, the switching valve, has heretofore been designed as a solenoid controlled or actuated valve. In the conventional split brake system then, this would require two solenoid actuated valves, i.e. one for each side of the brake system.